This is what I did when my fresh FreeBSD install didn't have network driver but there was a kmod available in the pkgs.

I used another machine to download pkg(8) and the missing kmod. To find the correct package names I checked "packages" section on freshports website. In my case I was looking for FreeBSD:15:quarterly, amd64. I needed pkg-2.4.2.pkg and realtek-re-kmod-1100.00.1500068_1.pkg.

I used pkg.freebsd with the following URL schema to download the files: https://pkg.freebsd.org/FreeBSD:15:aarch64/quarterly/All/<pkg_name>.pkg

I used a USB thumb-drive formatted with FAT32 and moved downloaded files there. Then I was ready to go back to the machine that was offline.

dmesg | tail
mkdir -p /mnt/usb
mount -t msdosfs /dev/da0s1 /mnt/usb
cp -R /mnt/usb/ tmp/

tar xf pkg-2.4.2.pkg
usr/local/sbin/pkg-static add pkg-2.4.2.pkg

This is a chicken-and-egg situation. We need to pkg to install pkg. ¯\_(ツ)_/¯

pkg add realtek-re-kmod-1100.00.1500068_1.pkg

# /boot/loader.conf
if_re_load="YES"
if_re_name="/boot/modules/if_re.ko"

# /init/rc.conf
ifconfig_re0="DHCP"